Content inspection and archive walks on seeding nodes (relay)

Inspection is split into prepare (database), probe (lib/content/probe:
downloads, decoding and parsing, no database) and apply (database).
worker:collection runs all three; seed:node with SEED_INSPECTORS leases
jobs from the same queues through the seed API (BullMQ manual leases),
fetches articles through the seed API and posts the probes back.

A node now needs only SEED_URL and SEED_TOKEN: the settings the app
requires but a node never uses get placeholders for seed:node.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/sevenzip/list.ts

@@ -0,0 +1,171 @@
+import { execFile } from 'node:child_process'
+import { mkdtemp, open, rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import path from 'node:path'
+import { promisify } from 'node:util'
+import { decodeSegment, type DecodedSegment } from '../yenc/index.js'
+import type { RarInfo } from '../rar/parse.js'
+import type { BodyFetcher } from '../rar/segment_reader.js'
+import {
+  checkHeader,
+  encodedHeaderEncrypted,
+  listingStart,
+  parseBsdtarListing,
+  parseSevenZipStart,
+  type SevenZipStart,
+} from './index.js'
+
+const run = promisify(execFile)
+
+/** The tail read for a listing: header plus packed header; more is not a header. */
+const MAX_TAIL_BYTES = 16 * 1024 * 1024
+
+/**
+ * Lists a 7z archive, also a split one (.7z.001, .002, …), from the first
+ * segment of the first volume (`firstData`, decoded) and the last segment(s)
+ * of the last one (CONCEPT.md D19). Those bytes are put at their place in a
+ * sparse file the size of the whole archive, which bsdtar (libarchive)
+ * lists: it only reads the start and the header at the end. Null when it
+ * isn't a 7z start, or the tail doesn't hold the header its start points to.
+ */
+export async function listSevenZip(
+  firstData: Buffer,
+  volumeCount: number,
+  lastVolume: { number: number; id: string }[],
+  fetch: BodyFetcher,
+  warn: (message: string) => void = () => {}
+): Promise<RarInfo | null> {
+  const start = parseSevenZipStart(firstData)
+  if (!start) return null
+  const split = volumeCount > 1
+  if (start.headerSize === 0) return sevenZipInfo([], false, false, split)
+
+  const tail = await readTail(lastVolume, start, fetch)
+  if (!tail) return null
+  // Encrypted headers (-mhe): known from the header alone, no listing possible (most 7z uploads).
+  if ('headersEncrypted' in tail) return sevenZipInfo([], true, true, split)
+
+  const dir = await mkdtemp(path.join(tmpdir(), '7z-'))
+  try {
+    const archive = path.join(dir, 'archive.7z')
+    const handle = await open(archive, 'w')
+    try {
+      await handle.write(firstData, 0, Math.min(firstData.length, start.archiveSize), 0)
+      await handle.write(tail.data, 0, tail.data.length, tail.from)
+      await handle.truncate(start.archiveSize)
+    } finally {
+      await handle.close()
+    }
+    return await bsdtar(archive, split, warn)
+  } finally {
+    await rm(dir, { recursive: true, force: true })
+  }
+}
+
+/** Lists the sparse archive; a trial extraction of one entry tells whether its data is encrypted. */
+async function bsdtar(archive: string, split: boolean, warn: (message: string) => void): Promise<RarInfo | null> {
+  let stdout = ''
+  try {
+    stdout = (await run('bsdtar', ['-tvf', archive], { timeout: 60_000, maxBuffer: 32 * 1024 * 1024 })).stdout
+  } catch (error: any) {
+    if (/header is encrypted/i.test(String(error.stderr))) return sevenZipInfo([], true, true, split)
+    warn(`bsdtar could not list a 7z archive: ${String(error.stderr || error.message).trim()}`)
+    return null
+  }
+  const entries = parseBsdtarListing(stdout)
+  const sample = entries.filter((e) => !e.directory).sort((a, b) => a.size - b.size)[0]
+  let encrypted = false
+  if (sample) {
+    try {
+      await run('bsdtar', ['-xOf', archive, sample.name], { timeout: 30_000, maxBuffer: 4 * 1024 * 1024, encoding: 'buffer' })
+    } catch (error: any) {
+      // Without the data (it's all zeros here), anything else fails too: only this message counts.
+      encrypted = /content is encrypted/i.test(String(error.stderr))
+    }
+  }
+  return sevenZipInfo(entries, false, encrypted, split)
+}
+
+export function sevenZipInfo(
+  entries: { name: string; size: number; directory: boolean }[],
+  headersEncrypted: boolean,
+  encrypted: boolean,
+  split: boolean
+): RarInfo {
+  return {
+    format: '7z',
+    volume: split,
+    firstVolume: true,
+    solid: false,
+    headersEncrypted,
+    truncated: false,
+    next: 0,
+    entries: entries.map((e) => ({
+      name: e.name,
+      size: e.size,
+      packedSize: 0,
+      directory: e.directory,
+      encrypted: encrypted && !e.directory,
+      splitBefore: false,
+      splitAfter: false,
+      stored: false,
+      dataOffset: 0,
+    })),
+  }
+}
+
+/**
+ * The archive's tail from the last volume: the header (checked against its
+ * CRC) and, for an encoded header, the packed stream before it. `from` is
+ * its position in the whole archive.
+ */
+async function readTail(
+  last: { number: number; id: string }[],
+  start: SevenZipStart,
+  fetch: BodyFetcher
+): Promise<{ from: number; data: Buffer } | { headersEncrypted: true } | null> {
+  const ids = new Map(last.map((s) => [s.number, s]))
+  const numbers = [...ids.keys()]
+  if (numbers.length === 0) return null
+  const segments = new Map<number, DecodedSegment>()
+  const segment = async (n: number) => {
+    if (!segments.has(n)) {
+      const id = ids.get(n)?.id
+      if (!id) throw new Error(`part ${n} of the last 7z volume is missing`)
+      segments.set(n, decodeSegment(await fetch(id), { lenientSize: true }))
+    }
+    return segments.get(n)!
+  }
+
+  const lastNumber = numbers[numbers.length - 1]
+  const lastSegment = await segment(lastNumber)
+  const volumeSize = lastSegment.meta.begin.size
+  const volumeStart = start.archiveSize - volumeSize
+  const partBegin = (lastSegment.meta.part?.begin ?? 1) - 1
+  const partSize = lastNumber > 1 ? partBegin / (lastNumber - 1) : volumeSize
+  if (volumeStart < 0 || !Number.isInteger(partSize) || partSize <= 0) return null
+
+  // Bytes [from, to) of the whole archive, from the last volume's parts.
+  const read = async (from: number, to: number): Promise<Buffer | null> => {
+    if (from < volumeStart) return null
+    const a = from - volumeStart
+    const b = to - volumeStart
+    const pieces: Buffer[] = []
+    for (let n = Math.floor(a / partSize) + 1; n <= Math.floor((b - 1) / partSize) + 1; n++) {
+      const s = await segment(n)
+      const offset = (s.meta.part?.begin ?? 1) - 1
+      if (offset !== (n - 1) * partSize) return null
+      pieces.push(s.data.subarray(Math.max(0, a - offset), Math.max(0, Math.min(s.data.length, b - offset))))
+    }
+    const data = Buffer.concat(pieces)
+    return data.length === b - a ? data : null
+  }
+
+  const header = await read(start.headerStart, start.archiveSize)
+  if (!header || !checkHeader(start, header)) return null
+  if (encodedHeaderEncrypted(header)) return { headersEncrypted: true }
+  const from = Math.min(listingStart(start, header), start.headerStart)
+  if (start.archiveSize - from > MAX_TAIL_BYTES) return null
+  const data = await read(from, start.archiveSize)
+  return data ? { from, data } : null
+}